Griffiths singularities in unbinding of strongly disordered polymers

Griffiths singularities occurring in the unbinding of strongly disordered heteropolymers are studied. A model with two randomly distributed binding energies -1 and -v, is introduced and studied analytically by analyzing the Lee-Yang zeros of the partition sum. It is demonstrated that in the limit v -> infinity the model exhibits a Griffiths type singularity at a temperature T_G =O(1) corresponding to melting of long homogeneous domains of the low binding energy. For finite v >> 1 the model is expected to exhibit an additional, unbinding, transition at a high temperature T_M=O(v).